1. Field of the Invention
The present invention relates to the transmission and reception of data, and more particularly, to a method of transmitting and receiving data in an environment where a wired network and a wireless network are connected to each other using a relay portal.
2. Description of the Related Art
Recently, there is an increasing demand for ultra high-speed communication networks due to widespread public use of the Internet and a rapid increase in the amount of available multimedia data. Since local area networks (LANs) emerged in the late 1980s, the data transmission rate over the Internet has drastically increased from about 1 Mbps to about 100 Mbps. Thus, high-speed Ethernet transmission has gained popularity and wide spread use. Currently, intensive research into a gigabit speed Ethernet is underway. An increasing interest in the wireless network connection and communication has triggered research into and development of wireless LANs (WLANs), greatly increasing availability of WLANs to consumers. Although use of WLANs may reduce performance in view of lower transmission rates and poorer stability as compared to wired LANs, WLANs have various advantages, including wireless networking capability, greater mobility and so on. Accordingly, WLAN markets have been gradually growing.
With the ever-growing demand for increasing the amount of data transmitted over networks and with recent developments in wireless transmission technology, the IEEE 802.11a, 802.11b, 802.11g, 802.11n, and 802.11s standards have been suggested. These standards are improved versions of the IEEE 802.11 standard, which is an initial WLAN standard defining WLANs offering a transmission speed of 1-2 Mbps. Standardization among the IEEE 802.11a, 802.11b, 802.11g, 802.11n, and 802.11s standards has already been completed or is underway.
However, there still exists a physical and economical limit in establishing a network environment based solely on wireless networks. Therefore, various methods have been suggested for establishing a network environment by coupling wireless networks and wired networks, thereby expanding the entire network environment and reducing the development costs.
FIG. 1 is a diagram illustrating a conventional network topology configured by wireless mesh networks. Referring to FIG. 1, mesh portals 11 and 12 are relay devices which connect a wired network and a wireless network and both have a wireless interface and a wired interface. Mobile nodes (MNs) 15, 16, 17, and 18 only have a wireless interface for accessing a wireless network. A mobile node can be connected to a mesh portal via a wireless network and can be connected to a wired network via the mesh portal. Mesh portals and MNs may serve as access points (APs), in which case, they may directly connect MNs to each other via a wireless network. Referring to FIG. 1, the MN 18 serves as an AP and thus configures its own basic service set (BSS).
Conventionally, in order to prevent a loop 14 from being generated in the network topology illustrated in FIG. 1, the mesh portals 11 and 12 have their own unique identifiers and broadcast them to a predetermined wireless network. Then, MNs existing in the predetermined wireless network receive the unique identifiers of the mesh portals 11 and 12 and choose one of the mesh portals 11 and 12. Thereafter, the MNs transmit and receive only broadcast packets transmitted by other MNs which choose the same mesh portal as the one chosen by the MN doing the transmitting and receiving. Another way of preventing generation of a loop 14 is to transmit broadcast packets via only a single portal. In the case of forwarding unicast packets, MNs transmit the unicast packets to a wired network via its chosen portal. Then, the chosen portal forwards only packets transmitted by MNs which exist in a wireless network and choose the same.
FIG. 2 is a diagram illustrating a conventional network topology in which two separate wired networks are connected to a single wireless network.
In a network topology illustrated in FIG. 2, a wireless network is divided into 3 groups 31, 32, and 33 which are managed by mesh portals 21, 22, and 23, respectively. The wireless network operates normally when only one wired segment exists. However, when separate wired segments exist, the wireless network may not operate properly because, while choosing a mesh portal, MNs may block transmission of broadcast packets by MNs belonging to another mesh portal or because MNs transmit unicast packets via only one mesh portal. For example, an MN 24 that chooses the mesh portal 23 which is connected to a lower wired network cannot transmit unicast packets to an upper wired network even though it can still transmit data to the mesh portals 21 and 22 in a wireless manner.
Therefore, if a mesh portal is chosen as a connection to a wired network in order to prevent a loop, it may be difficult to transmit data to another wired network. However, if no mesh portal is chosen as a connection to a wired network, a loop is likely to be generated. Therefore, it is necessary to develop methods and apparatuses for transmitting data to a wired network while preventing a loop from being generated.